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I have a few petris with EQ tisssue samples. I keep getting mad condensation on the lids, its getting on the mycilium too!1 it gets the mycilium all wet yet it continues to grow. the water makes the mycilium loook very light colored(yes im sure its mycilium). the humidity in my house is 33%, i have not set up an incubator so they sit under a blanket at fluctuating temps. where is this condisation comming from? could it be the agar? this hapen to anyone else? again the mycilium is growing steadily but it is clearly wet!1

I bet when you mixed your agar you added too much water. As long as contams don't develop your OK. I would transfer a bit to a new petri w/ correct water content if you worried. If you are undertaking agar it's a good idea to always have a few extra plates in the fridge to work with. Good luck!

Condensation is normal for petri dishes. The humidity comes from the agar and is wanted, else your mycellium would rather not grow at 33 % rH!

Yours have much condensation because the dishes are subjected to variations in the temperature. Especially if the air is almost saturated with water vapour, i.e. >90% rH (inside the petri of course), a small downward variation of the temperature oversaturates the air, and therefore the water vapour has to condensate.

Pobably you are also useing glass petris, which tend more to get condensation as the plastic ones. This is because of the higher heat conductivity of glass.

Don't worry about the condensation, unless the mycellium is turning blue - a sign that it is being harmed. The only problem about condensation is that a bacterial contamination can be spread easily and fast throughout the whole petri dish.

If you should have such problems, then try to mantain the petri dishes at a constant temperature, e.g. at 20 - 22 C, to prevent heavy condensation.

Also when you pour the agar at a high temperature, you get condensation. Therefore the prefered pouring temperature is only some degrees celcius above the hardening temperature, i.e. pour at about 45 C. This reduces much of the initial condensation.

Elektrolurch

--------------------"For all the time spent in that room
The doll's house, darkness, old perfume
And fairy stories held me high on
Clouds of sunlight floating by.", Pink Floyd '67